Definitely. As a minimum we'd need to know what programming language you're using, and ideally see the code. Some questions: is your sever sending nulls, or are the clients just printing nulls because nothing is being received? How did you try debugging your app, and are you certain your server is even trying to send more messages? There is definitely no "one message per client" limitation.
Also, I suspect this should be in the programming forum, not newbie.